Method of heat-treatment of aluminum alloys

ABSTRACT

A method of heat treatment of aluminum alloys of the type Al-MgSi for the purpose of improvement of the processibility by extruding, which comprises the steps of subjecting said alloys to a homogenization-glowing at 530*C to 580*C, and cooling and alloys to a temperature range of 230*C to 270*C, while maintaining a substantially uniform temperature gradient. The cooling step takes place at a speed of at least 100*C/h without quenching, and a holding period is maintained within the temperature range of 230*C to 270*C, for a time period of about 4 to 24 hours, whereupon further cooling or heating to working temperature of said alloys is performed.

.United States Patent [191 Warbichler, deceased et al.

[ METHOD OF HEAT-TREATMENT OF ALUMINUM ALLOYS [22] Filed: May 22, 1972 [21] Appl. No.: 255,511

Related US. Application Data [63] Continuation-impart of Scr. No. 806,926, March 13.

1969, abandoned.

[52] US. Cl. 148/159, 148/115 R, 148/127 [51] Int. Cl. C22f 1/04 [58] Field of Search 148/115, 12.7, 159

[56] References Cited UNITED STATES PATENTS 2.695.253 11/1954 Schaaber 148/159 1 June 11, 1974 Primary ExaminerCharles N. Lovell 5 7 ABSTRACT A method of heat treatment of aluminum alloys of the type Al-Mg-Si for the purpose of improvement of the processibility by extruding, which comprises the steps of subjecting said alloys to a homogenization-glowing at 530C to 580C, and cooling and alloys to a temperature range of 230C to 270C, while maintaining a substantially uniform temperature gradient. The cooling step takes place at a speed of at least 100C/h without quenching, and a holding period is maintained within the temperature range of 230C to 270C, for a time period of about 4 to 24 hours, whereupon further cooling or heating to working temperature of said alloys is performed.

6 Claims, 2 Drawing Figures sum 1 OF 2 PATENTEUJUN] 1 I974 FIG.

slelellso PATENTEDJUN 1 1 I974- SHEET 2 0f 2 FIG.

The present invention is a continuation-in-part of the co-pending patent application Ser. No. 806,926, filed Mar. 13, 1969 now abandoned.

The present invention relates to a method of heat treatment of aluminum alloys having the DIN characteristics AlMgSi 0.5 dek and AlMgSi 1, respectively,

which have the following compositions: Mg 0.4 0.9 and 0.6 1.4, respectively; Si 0.3 0.7 and 0.6 1.6, respectively; Fe 0.4 and 0.5, respectively; Mn 0.3 and 1.0, respectively; Cr 0.05 and 0.3, respectively. The rest is remainder of aluminum and unavoidable impurities.

The heat treatment in accordance with the present invention has the purpose to improve the processibility characteristics of the mentioned alloys in extruders.

Methods for heat treatment of alloys of the type of AlMgSi are known in which the material is subjected to a conventional homogenizing glowing within the range of 530C 580C, whereupon the material cools off with a temperature gradient of less than 50C/h, preferably of 20C/h to about 250C. The thus treated materials can then be heated up to a hot fabrication temperature of 350C to 530C for the purpose of extruding. In this treatment, many of the dissolved ingredients of Mg and Si can be precipitated in coarse form.

It is not the aim of the present invention to obtain such structure. During the investigations, which have guided to the present invention, it has been found rather, that the desired improvement of the processibility characteristics are obtained then particularly for ex-' truding when possibly many of the solved ingredients of Mg and Si are separated in form of finest particles, which are to a great extent coherent with the Al matrix and during heating to extensive temperature do not go completely in solution, but rather break during the molding and during the following hot settling can be-effective as a nucleus for the precipitation.

' It is one object of the present invention to provide a method for heat treatment of aluminum alloys, wherein the alloys in conventional manner are subjected to a homogenizing glowing at 530C 580C, and thereafter are cooled by maintaining a substantially uniform temperature gradient to a temperature within the range of 230C to 270C, the cooling taking place at a speed 4 of at least 100C/h, (or cooled by maintaining a subabout 8 h. In case of longer holding in the mentioned range, in other words no essential or appreciable structure change takes place any more. For some working purpose, however, already, a part structural variation of the desired type is sufficient: in such cases, shorter holding time. periods can suffice.

If desired, the glowing and the following tempering can be repeated under circumstances during different time periods.

In this connection it should be mentioned that one cools from the given glowing temperature to the room temperature and thereafter to heat up again to tempering temperature; however, this variation of the heat treatment requires totally rather long treatment times.

With these and other objects in view, which will become apparent in the following detailed description, the present invention will be clearly understood in connection with the accompanying drawing, in which:

. FIG. 1 is a 2100 times enlargement of a testing material; and

FIG. 2 is an enlargement of the surface structure ob tained by applying the method of the present invention.

Referring now to FIG. 1, a 2100 times enlargement of a tube consisting of an Al-Mg-Si-alloy of the type marked as P 568 is disclosed. The surface has been as conventional metallographically preworked, electropolished and chemically etched. The photo has been made in an emission electron microscope. The heat treatment of the sample has been performed in accordance with the statements given in the German patent publication No. 1,247,030, namely one hour at 570C to 580C homogenized, thereafter cooled within 330 minutes down to 300C (temperature gradient 50C/h) and thereafter cooledoff in air. The structure of the surface shows comparatively few irregularly distributed material separations.

Referring now to FIG. 2, the preparation of the sample shown therein took place in the same manner as disclosed in connection with FIG. 2, with the same material. The heat treatment consisted of a homogenization for one hour at 570C to 580C. Thereafter, the sample has been cooled off within 60 minutes to about 250C (temperature gradient of at least 100C/h). Thereafter, for 24 hours the temperature was maintained at 250C and then coolingoff took place in the air. Referring againv to FIG. 2 of the drawings, the surface structure is completely different from that obtained in the known methods. One recognizes the fine uniform needle-like characterized separations divided over the entire surface, which separations correspond with the abovestated requirements. It is, undoubtedly apparent, that the compared methods differ from each other not only formally, but lead metallurgically to completely different results.

It is to be understood, that in case longer treatment 7 time periods are taken in stride, the indicated temperature ranges of the glowing and of the tempering can be undercut. Such measures do not bring about basically and economically advantages, are, however, within the frame work of the present invention.

While we have disclosed one embodiment of the present invention it is to be understood that this emsubjecting said alloys to a homogenization-glowing at 530C to 580C,

cooling said alloys to a temperature within the range of 230C to 270C, while maintaining a substantially uniform temperature gradient,

said cooling step taking place at a speed of at least 100C/h without quenching,

maintaining a holding period of about 4 to 24 hours within said temperature range of 230C to 270C, and

further cooling said alloys.

2. The method, as set forth in claim 1, wherein said holding period is maintained for about 8 hours.

3. The method, as set forth in claim 1, wherein said holding period is maintained for about 24 hours.

4. A method of heat treatment of aluminum alloys of the type Al-Mg-Si for the purpose of improvement of the processibility by extruding, comprising the steps of subjecting said alloys to a homogenization-glowing at 6. The method, as set forth in claim 4, wherein said holding period is maintained for about 24 hours.

UNITED STATES PATENT )FFICE CERTIFICATE OF CORRECTION Patent No. 3,816,190 Dated June J 97 Inventor s Peter Warbichler, Deceased It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

On the Title page, in item "Ingrid Frai'oli," fn'ee Warbichler" should read Ingrid Fraiol i ,1 nee Warbichlerand the assignee j should read: Firma Zentrum- Fur Elektronenmikrosko pie, Austria (and) Firmal Vereinig'te Metallwerke Ranshofenberndorf Ak'tiengesell'eohaft, Austria Item [55} should ream-method of Heat-Treatme t or-Aluminum s 3 Alloys---- vSigned and sealed this 7th day of ianuary fll975.

Attest:

MCCOY M. GIBSON J I c, MARSHALL DANNTK Attesting Officer Commissioner of Patents FORM P941050 10-69) 4 QSICOMQDC 5 UI$.GO;IERNHEN:T riz mnus orrlcz: 869 93 I UNITED "STATES PATENT OFFICE I CERTIFICATE OF CORRECTION June 11, 1974 Patent No.5 3,816,190 I Dated of. a]. It is certified that error appears in the above-identified patent anii that said Letters Patent are hereby corrected as shown below:

On the cover sheet item I76] cancel the assignee's name from the names of the inventors, and insert,

- [7.3 Assignee: Firma Vereinigte Metallwerke Ranshofen- Berndorf Aktiengesellschaft, Ranshofen,

Austria Signed and sealed this 1st day of October 1974.

(SEAL) Attest:

McCOY M. mason JR. c. MARSHALL DANN Attesting Officer Commissioner of Patents UICOMM'DC OSU P" IJYI! GOVIINMINY PRINTING OIIICI: as. so 

2. The method, as set forth in claim 1, wherein said holding period is maintained for about 8 hours.
 3. The method, as set forth in claim 1, wherein said holding period is maintained for about 24 hours.
 4. A method of heat treatment of aluminum alloys of the type Al-Mg-Si for the purpose of improvement of the processibility by extruding, comprising the steps of subjecting said alloys to a homogenization-glowing at 530*C to 580*C, cooling said alloys to a temperature within the range of 230*C to 270*C, while maintaining a substantially uniform temperature gradient, said cooling step taking place at a speed of at least 100*C/h without quenching, maintaining a holding period of about 4 to 24 hours within said temperature range of 230*C to 270*C, and heating to extrusion working temperature of said alloys.
 5. The method, as set forth in claim 4, wherein said holding period is maintained for about 8 hours.
 6. The method, as set forth in claim 4, wherein said holding period is maintained for about 24 hours. 